The present invention relates to a burner apparatus for smelting furnaces, and more particularly to an auxiliary combustion apparatus for electric furnaces.
Auxiliary combustion apparatus are known for directly burning a mixture of oxygen and fuel oil, kerosene or the like in such a furnace to smelt the charge effectively and rapidly and thereby achieve improved productivity and savings in power.
Auxiliary combustion burner apparatus for smelting furnaces, especially for electric furnaces, include the movable type and the fixed type.
FIGS. 1 (1) and (2) show a movable burner apparatus, which has the following construction.
With reference to these drawings, a furnace wall 2 surrounding electrodes 1 is formed with a burner inserting bore 3. The tip 5 of a burner body 4 having a fuel nozzle, an oxygen nozzle, etc. is movable into and out of the bore 3 by piston-cylinder means 6.
For combustion, the piston of the means 6 is forced out to insert the tip 5 into the bore 3 as seen in FIG. 1 (1). When the burner is not in use, the piston of the means 6 is retracted to hold the tip 5 away from the bore 3 as seen in FIG. 1 (2), and compressed air is supplied from a compressor or blower through the burner body 4 to prevent the inserting bore 3 and the burner nozzles from clogging up with splashes and slag from the interior of the furnace.
With the conventional apparatus, however, a large amount of air is required for purging and therefore consumes energy, and the air forced into the furnace results in a great heat loss and adversely affects the metallurgical reaction.
To eliminate these problems, it is attempted to provide a splash blocking plate 7 in front of the tip 5 as shown in FIG. 1 (2), but in this case there arises the problem that splashes will accumulate in the burner inserting bore 3.
In addition to these problems, it is impossible to completely prevent the molten charge and slag from splashing out from the furnace, so that the bore is manually cleaned after the discharge of the molten material. However, this requires a heavy labor at a high temperature and is inefficient.
Further when a bumping phenomenon occurs within the furnace, molten steel and slag flows out through the burner inserting bore 3, causing damage to the burner apparatus.
To overcome these drawbacks of the movable burner apparatus, a fixed burner apparatus has been proposed as seen in FIG. 2. The burner body 4 of the apparatus is provided with a tip 5 having a fuel nozzle, oxygen nozzle and a purging air nozzle and fixedly installed in a burner inserting bore 3 of a furnace wall 2 surrounding electrodes 1.
The fixed apparatus is adapted to prevent the outflow of molten steel and slag but has the necessity of purging the burner at all times to prevent the nozzles from clogging.
Since the burner apparatus is used only for auxiliary combustion, it is used only for 20 to 40% of the operating period of the furnace and must therefore be purged with air for the remaining 60 to 80% of the period. Consequently the air cools the interior of the furnace, produces an extremely serious adverse effect on the metallurgical reaction and entails a seriously reduced combustion efficiency.